linux-kernel - [PATCH V2 15/20] cxl: Add a routine to find cxl root decoder on cxl bus using cxl port

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Message-Id: <20250730121209.303202-16-s.neeraj@samsung.com>
Date: Wed, 30 Jul 2025 17:42:04 +0530
From: Neeraj Kumar <s.neeraj@...sung.com>
To: linux-cxl@...r.kernel.org, nvdimm@...ts.linux.dev,
	linux-kernel@...r.kernel.org, gost.dev@...sung.com
Cc: a.manzanares@...sung.com, vishak.g@...sung.com, neeraj.kernel@...il.com,
	Neeraj Kumar <s.neeraj@...sung.com>
Subject: [PATCH V2 15/20] cxl: Add a routine to find cxl root decoder on cxl
 bus using cxl port

Add cxl_find_root_decoder_by_port() to find root decoder on cxl bus.
It is used to find root decoder using cxl port.

Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
---
 drivers/cxl/core/port.c | 27 +++++++++++++++++++++++++++
 drivers/cxl/cxl.h       |  1 +
 2 files changed, 28 insertions(+)

diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index ba743e31f721..c1bb0e0286ed 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -524,6 +524,33 @@ struct cxl_switch_decoder *to_cxl_switch_decoder(struct device *dev)
 }
 EXPORT_SYMBOL_NS_GPL(to_cxl_switch_decoder, "CXL");
 
+static int match_root_decoder(struct device *dev, const void *data)
+{
+	return is_root_decoder(dev);
+}
+
+/**
+ * cxl_find_root_decoder_by_port() - find a cxl root decoder on cxl bus
+ * @port: any descendant port in CXL port topology
+ */
+struct cxl_root_decoder *cxl_find_root_decoder_by_port(struct cxl_port *port)
+{
+	struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
+	struct device *dev;
+
+	if (!cxl_root)
+		return NULL;
+
+	dev = device_find_child(&cxl_root->port.dev, NULL, match_root_decoder);
+	if (!dev)
+		return NULL;
+
+	/* Release device ref taken via device_find_child() */
+	put_device(dev);
+	return to_cxl_root_decoder(dev);
+}
+EXPORT_SYMBOL_NS_GPL(cxl_find_root_decoder_by_port, "CXL");
+
 static void cxl_ep_release(struct cxl_ep *ep)
 {
 	put_device(ep->ep);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 129db2e49aa7..e249372b642d 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -857,6 +857,7 @@ struct cxl_nvdimm *to_cxl_nvdimm(struct device *dev);
 bool is_cxl_nvdimm(struct device *dev);
 int devm_cxl_add_nvdimm(struct cxl_port *parent_port, struct cxl_memdev *cxlmd);
 struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_port *port);
+struct cxl_root_decoder *cxl_find_root_decoder_by_port(struct cxl_port *port);
 
 #ifdef CONFIG_CXL_REGION
 bool is_cxl_pmem_region(struct device *dev);
-- 
2.34.1